The fonts will be located where the user has chosen, and may be spread about, as different programs will store them in different locations, but most now both install them, and place the files in the OS's fonts folder. Those will likely be backed up with a system back up.

As far as Brushes, Actions, Scripts, plug-ins, etc., those will be in the program's folder hierarchy, unless the user has chosen to Save some of those assets into a separate folder, say My Documents\Hunt's Brushes, and then loaded from there..

I had always thought that when it came to fonts, there was a folder where Adobe products looked for them (rather than the default system one I have at C:\Windows\Fonts)

Sadly, I have used the, what is it? Preferences editor (probably wrong words) to load in things like tool presets from other locations.

That has me thinking. Aside from the default resources PS uses, if I am capable of specifying an external location for my other resources that is in a folder where I'm already backing up, then I'll be automatically backing up those files without need for finding their locations in the C:\Program Files\Adobe\Photoshop subfolders.

I had always thought that when it came to fonts, there was a folder where Adobe products looked for them (rather than the default system one I have at C:\Windows\Fonts)

No, Adobe products rely on the installed system fonts. Now, and cannot tell you if the installation discs still include some fonts (OpenType now), but to use those, one would Install them in the system. Going back many years, Adobe programs used to copy folders of fonts to the machine, and then would install those into Windows. I have not seen that practice, in a very long time. That practice also could spread fonts all around, which is not really a good thing, for many reasons. First, because they are spread, and were often in the program's folder hierarchy, one had difficulty backing them up. Then, if say one had installed PageMaker, Illustrator and Photoshop, and each had the same fonts, one would have triplicates of those fonts, just taking up space.

I have nearly all of my fonts in several folders on C:\, such as PS Fonts, TT Fonts, OT Fonts, and in the Windows font folder, only have my base fonts. All of the others are managed by Extensis Suitcase, and I just activate from those storage folders, or deactivate, as needed. If I have not activated any but that base set, then that is all that PS will see. Once activated (say a project's, or client's "font set," then PS sees those, until I deactivate that font set.

This also makes backing up my fonts easy, as I just do a DVD-Data of my fonts folders, and can migrate from machine, as I build one, or just have the backup, in case something goes bad. Over the decades, I have paid a lot for those fonts, and do not want to loose them.